Brake adjustment mechanism



Dec. 31, 1957 R. PHILLIPS BRAKE ADJUSTMENT MECHANISM "2 Sheets-Sheet 1 Filed Oct. 1, 1954 IN V EN TOR. Po Y Pff/1.1. /Ps BY Q i J f, y,

4r weNEYS Dec. 3l, 1957 R. PHILLIPS 2,818,143

BRAKE: ADJUSTMENT MECHANISM Filed Oct. 1, 1954 2 Sheets-Sheet 2 2a 21 f /y/A United States Patent i 2;-818543 BRAKE ADJUSTMENT MECHANISM Roy Phinips,chagrin raus, ohio Application October 1, .19.54, Serial No.v459,708

12 claims. (ci. iss-1%) v The present invention .relates to clearance .adjusting devices, 4especially lautomatic brake clearance"adjusting devices, and, more particularly, to an automatic brake clearance .adjusting `device of ythe type .adapted `to aantomatically provide `a predetermined clearance 'between a retracted brake shoe and afbrake drum which .device icontains automatic rmeans for preventing the device from adjusting itself in .response vto an increase in clearance between the brake 'shoe and the brakedrum produced as aresultof thermal expansion of the brake d1-um.

An object of the present :invention `is the provision of .a vnew .and improved .clearance .adjusting .device having `means which prevents the .device from operating .to adjust .clearance between twospaced members at .temperatures above v.a .predetermined level.

Another .objectof the present invention is vthe'provfision of .a new and improved automatic 'brake clearance yadjusting device which device contains automatic means 'for preventing the vdevice from operating .to ychange the lclearance between .a brake .drum and a retracted .brake .shoe when the brake vdrum or Ithe interim thereof .is at .temperatures above a gpredt-:termined flevel.

Astill further object of the invention .is the provision of a new and improved `automat-ic .clearance .adjusting device of ,the .type .comprising iirst and .second members .at least one of which is suitably supported for'movement toward and a-waytrom .the othermember, a .third member movably supportedfon said iirst member and .adapted ,to limit movement of said second member toward'saidiirst member, means for advancing -said third member toward -said secondlmernber whenever the second member-.is more than a predetermined distance from said third member, and .temperature responsive means rendering sa'id `rst mentioned means inoperative at temperatures above a predetermined temperature.

`The "furtherobjects andadvaritagesof `the invention will be apparent to `those skilled'in the yartto'which the invention relates 'from the .description 'of the following'embodiments described with reference Lto the accompanying "drawings forming apart Vof this specification, in which similar reference charactersdesignate correspondifgv Parts, and'in which:

Fig. lis a 4fragmentary elevational viewo'f a hydraulic `friction brake embodying 'the "present invention;

Pig. T2 'is an Venlarged sectional view taken along line 2-2 of'Fig. 1 and Vshowingthef'brake adjusting mechanismiin the nonbrking "orl retracted position;

TFig. f3 is a view .similar to Fig. .2 `bu`t showing the adjusting mechanism fin' the braking position;

Fig. .2l 'is a vsectional view'taken approximately on 'the line 1*21 v'of Fig. '72;

"'fFig. S is a 'sectional view taken approriimately along the lineS-LS Aofi'iigfZ; v

Fig. '6 is 'a longitudinal "sectional'view siniilar'to Fig 3 'but"embodying 'a' bellows itypeo'f 'tliermostatic unit, `and "Whilethe rpre'sent iinvention isfapplicable "Ito' various Qatented Dec. 31, 1957 ICC types of .clearance adjusting devices, it is herein shown .as .embodied :in .a device-for `automatically adjusting the retracted v.positionsof .the brakes of an .automotive vehicle. According .to .the-provisions ofthe present invention, the device includes temperature `responsive or therrnostatic means for preventing the device from automatically compensating for changes Vin clearance between members, which clearance the device is adapted vto control, when -.these -changes are lproduced as a result of "thermal eX- pansion. The Atemperature responsive or thermostatic means utilized to control the operation of the vclearance adjusting device may be any one of a `number of types, for example, bimetallic `elements and bellows and other type expansionfunits or chamberspof various kinds, including gas .or 'liquid filled, -or containing a low boiling ,point liquid, thatis, vapor lled,'and the detailed applica- -tion of several Lwill be hereinafter described.

The embodiment of the invention shown in Figs. l through 5 .of the drawings usesa bimetallic element type of thermostatic means. The 'brake shown comprises a brake drum 1,0, bra-ke shoes 11, 12 provided with brake linings 13. The .brake shoes are pivotally mounted at a point, not shown, for movement to braking position b y a hydraulic cylinder 15 located intermediate 'the upper, adjacent,-spaced ends `of vthe ybrake shoes. When pressure is applied to the cylinder, lhyllraulic plungers 16l engaging the upper ends yof the shoes move outwardly to expand the shoes and pressl-.the lining 13 into engagement with .the brake drum, as kshown .in Fig. l. A retracting spring 17 connected to the brake shoes adjacent to the brake cylinder pulls the 'brake'slioes back into their nonbraking In order for the brake to function satisfactorily, it is desirable to have'and maintain a predetermined clearance between lthe -brake drum .and the brake .lining when the .brake is in its 'noribraking'ppos'ition The clearance, however,`between'the lining and the drum will become greater as the brake is used due to the wear of the lining. The adjusting mechanism or device, designated generally as 18, automatically maintains a predetermined clearance between the lining :and the brake drum as wear occurs, by determining the .point to which .the spring 17 returns the brake shoes "11, 12. The device is preferably constructed as a unit that `may be quickly and easily attached to a conventional friction brake and is so shown 'inthe drawings, l

The adjusting 'device .18 comprises a tube or sleeve 20 having slidably 'supported .therein coaxial members 21, 22 positioned 'inend-to-end `relationship with their outer ends connected tothe shoes '12, "11, respectively, The minimum spacingbetween the members 21, 22 is `controlled by a spacing or abutment member "23lthreaded into member `21and providedwith a shoulder 24 on a part projecting .therefrom adapted 'to vabut and compress a bimetallic element 25 4the operation of which will later bedescribed, between itself and the inner end of .member 22. The .spring `17, in absenceof overriding pressure in cylinder I5, will move the 'upper ends of the 'brake shoes 11, 12 toward each other until the member 22 completely .collapses .the vbimeta/llic lelement '25 `between itself and the `s"lioulder'24 on 'the`me'n`1'ber23fas shown in'Fig. 2, thereyby preventing further inwardmove'ment. The elective length 'of the members' '21, 22 and the spacing member 23 determine's'the distance Lbetween -the outer ends of the members 21,'22'wl1en`tl1ebr`ake'is in its .nonbra'king position, and conseqnently'the'brake clearance. The members "21, '22fi`1t :closely within the Vtube 20 'but are .freely 'theiopp'os'ite ends ofitliet-ubet) are provided with'mount- 1ing pins -II26 dap'ted to" be-inserted l'into V4drilled apertures inithe brake shoes and secured therein by snap rings 27.

l panded position.

When pressure is applied to the cylinder to move the brake shoes to their braking position, the member 22 and the shoulder 24 on the member 23 will he moved apart, see Fig. 3. The free distance or space between the member 22 and the shoulder 24 i. e. the distance between member 22 and shoulder 24 less the compressed thickness of the bimetallic element 25 when the shoes are in their braking position, will be a function of the clearance between the brake shoes or linings and the brake drum when the brake shoes are in the nonbraking position, in which position the bimetallic element 25 is collapsed between the member 22 and the shoulder 24 on the member 23.

As wear occurs, the clearance between `the lining and the drum, and the free space between member 22 and the shoulder 24 on the member 23 tends to increase. The free space between member 22 and the shoulder 24 of the member 23 when in braking position and, in turn, the brake clearance are maintained constant by the turning or threading of the member 23 toward the member 22 to compensate for wear as it occurs. To this end, a torsion spring 29 within the member 21 is interposed between the member 23 and the right-hand pin 26. The spring 29 tends to rotate the member 23 so that it will be threaded outwardly of member 21 toward member 22. The rotation, however, of member 23 is prevented when the brake clearance is as desired by the engagement of the end of a rod 30 pinned or otherwise fixed to the member 23 with a disk-like member 31 located within and positioned transversely of the counterbored, left-hand end of the member 22. The rod 30 may, as in the illustrated embodiment, extend through the member 23 into member 21 and function as a guide rod for spring 29.

The member 31 is biased in a direction towards the end of rod 30 by a compression spring 33 within the member 22 intermediate the disk 31 and the left-hand pin 26. When the member 22 and the member 23 are moved apart, the rod 30 will be withdrawn, in part, from the member 22. The disk 31 will follow and maintain engagement with the rod 30 until it strikes the shoulder 34 at the bottom of the counterbore in the member 22 within which it is located. At this point, if the relative movement between member 23 and member 22 is continued, as is the case when wear occurs, the rod 30 will tend to lose contact with the disk 31 but will be prevented from so doing by the spring 29 which will thread the member 23 outwardly of member 21 to maintain engagement between the end of the rod 30 and the disk 31. A predetermined maximum free distance is, therefore, always maintained between the end or shoulder 24 of the member 23 and the member 22, which distance is equal to the length of that portion of the rod 30 extending beyond the shoulder 34 when the member 22 and member 23 are in abutting or nonbraking relationship. By proportioning the parts so that the rod 30 extends a distance beyond the shoulder 34, which is proportioned to the desired brake clearance when the member 22 and member 23 are in their abutting or nonbraking position, as is shown in Fig. 2, the proper brake clearance will be maintained as wear occurs by the automatic threading of member 23 outwardly to increase the spacing between members 21, 22.

Upon prolonged application of the brake suicient heat may be developed to expand the drum 10, in which event the brake shoes move outwardly accordingly. As the brake shoes move outwardly, the effective length of the members 21, 22 and the member 23 increases except for the imposition of the bimetallic element 25. As will be hereinafter explained, the member 23 would thread outwardly of the member 21, as previously explained, to take up the additional clearance with the result that when the brakes are released, the brake shoes 11,'12 would not return to their original position but to a slightly more ex- The predetermined clearance between `asian/.taf Y' r' the brake shoes and the brake drum would thus be maintained but upon cooling of the brake drum it would retract, reducing the clearance between it and the brake shoes and possibly eliminating the clearance altogether, in which event the brakes would be set or would bind. The heat produced by the application of the brakes and which causes the brake drum to expand may also produce a certain amount of expansion of the members 21, 22 and the member 23, but under normal circumstances the temperature of these parts would not rise in proportion to the temperature of the brake drum, with the result that the normal expansion and contraction thereof would not equal that of the brake drum.

According to the provisions of the present invention, temporary expansion of the brake drum due to heat created therein by prolonged application of the brakes is prevented from effecting the normal clearance desired and maintained between the brake shoes 11 and 12 and brake drum 10 by the incorporation or imposition of temperature responsive means in the abutment means which normally hold the member 23 against rotation by the spring 29, which temperature responsive means in the present embodiment comprises the bimetallic element or member 25, previously referred to, interposed between the righthand end of the member 22 and the abutment 24. The heat responsive bimetallic element 25 may be of any desired construction. As shown, it comprises a single coil of an annularly-shaped coil spring and assumes the appearance of a conventional, spring-type lock washer. The element is comparatively yieldable so that it can be collapsed by the spring 17 which biases the brake shoes. The bimetallic element 25 however, is of sufficient strength as compared to spring 29 that it can prevent spring 29 from advancing the member 23 when the opposite ends of the bimetallic element are contacted by shoulder 24 and member 22. Bimetallic element 25 is preferably designed to assume an expanded width at a predetermined normal temperature such that it will bridge the normal space between shoulder 24 and member 22 when shoulder 24 and member 22 are in their retracted positions in which event the member 31 and the spring 33 may be dispensed with. Upon a rise in temperature incident to prolonged application of the brakes, the temperature within the brake drum will rise as well as the temperature of the brake drum itself and the bimetallic element 25 is so designed that it will expand an amount equal to, or exceeding, the amount which the brake drum expands, thereby remaining in contact with shoulder 24 and member 22 and constituting abutment means supplementing the abutment formed by the parts 30, 31 and preventing the advancement of member 23. When the temperature of the device returns to normal, the bimetallic element 25 may collapse until it no longer bridges the normal or desired space between shoulder 24 and member 22 when the brakes are in their retracted position, and upon the next application of the brakes, the disk 31 again controls the advancement of member 23.

A second embodiment of the invention is shown in Fig. 6 wherein the duplicate parts are designated by the same reference characters previously employed and the corresponding but differently constructed parts by the same reference characters with a prime mark atixed thereto. In the embodiment shown in Fig. 6 of the drawing a bellows type, vapor lled temperature responsive or thermostatic unit 25' having a low temperature boiling point liquid therein is used instead of the previously described bimetallic element 2S. The bellows unit 25 may be any one of the previously described types and is shown as a bellows type vapor pressure unit positioned in a longitudinally extending chamber or bore 51 in the end of the rod 30' in a manner permitting one end of the bellows to expand outwardly against the disc 31.

The operation of this embodiment is quite similar to that of the preceding embodiment. The unit is shown in its normal brake-applying position, with the members "21 and .2'2'in :their"expanded 'jpositions. l"Upon "release of 'the brakes, member ".22 `is moved "into 'engagement withs'houlder 24 on `the end `of member'23 providing ybrake v.clearance A.proportional .to the .clearance 'between the `membersfshown in the .drawing Upon a rise in temperature incident Vto .prolonged .application --of lthe .brakesfbellows 725 -expands..outwardly beyond the end 52offthe member E30 fafgainstdisk 31 and prevents: mem- .:ber323 from beingadvanced towardrthe disk 31 by the spring `29fis free to advance .rod 30 until it again "enf gagesthe disk.

' A third embodiment `of the invention iss'hown'inFi'g; 7 in'whi'ch parts which area duplicate of those 'shown'n the previous `embodiments `are designated :by the same reference character and the corresponding jbut differently constructed :parts vare designated "by the `Ysame reference numeral :but with a double prime 'mark 'aixed'thereta The 'temperature 'responsive element '25 in 'this enibodiment comprises a 'vapor-'lled piston chamber "60 formed "by the telescoping of the open 'end 'of a tubular, 'cup- -shapedcylinder `61 over the end'ofrod 30. Cylinder 61 has aleng'th 'exceedin'gg'the distance 'betWeeni-the end of member '22 'and Ithe 'bottom ofthe counterbore-34'by an amount proportional to the braking clearance desiredand van O-ring 63 seated in a groove' 64 on the end 'o'f the.rod'30" provides sealing engagement between the rod Aand cylinder. In 'the 'normal brake-applying position shown in the drawing, the .projecting end of `cylindertl bears againstplate`31 with su'icientvpressure to hold the other end `of the cylinder in.engagement with abutment 24. Should wear occur, a subsequent application ofthe brakes causes surface 34 of member Z2 to lift plate '31 from Vthe end of cylinder "61 and permits spring 29 to advance members '23 until the projecting end of the cylinder againabuts the plate. Upon a riseintemperature inthis embodiment, an increase in 'vapor pressure in chamber l:60 lcauses .'thecylinder 261 to compress spring 33 and hold plate 31 out of engagement with surface 34. 'This `prevent-s spring -29 -from 'advancing member 23 until -such time as the "temperature `falls to 'or below normal. If wear has occurred, the next application of the brakes will cause plate 31 to be moved from the end of the cylinder 61 and member 23 will be advanced in a manner similar to that of previous embodiments.

It will be noted from the drawings that the tube 20 and the members 21, 22 are of maximum length consistent with the space limitations imposed by the size of the brake, thereby providing long, overlapping, sliding connections which permit free operation of the various parts and prevent any sagging and binding. The members 21, 22 float, so to speak, within the tube 20 and no binding forces or stresses are imposed upon the threaded connection between the member 21 and the member 23 other than those required to perform the desired operation. The projecting ends of members 21 and 22 are closed by plugs 35 to assure that the operating parts will remain free from dust and dirt. To aid in this regard, O-ring or other type seals may be positioned between tube 20 and members 21 and 22. This may preferably be accomplished by means of O-rings 40 and 41 positioned in annular grooves 42 and 43, respectively, in the outer ends of the tube 20.

If the adjusting mechanism, when installed, is adjusted so that the shoes have a greater clearance in their nonasma-42 6 braking position than that desired, the member 23 will "'beitthreaidedoutwardly'tthe :first time vthe Ybrakes are ap- `pliedtoautomatica'lly adjust the eective length of 'mem- 'bers "21,22 and mem'ber23 and thereafter the lining on the shoes-will jhave the desired proper clearance with respect tothe brake kdrum when returned to their 'nonbraking position.

v"The adjusting Amechanism may be assembled and vshipped with afwire'inserted through holes 44, 45 `and 46 in fparts'30, I"-22-and"`-20, respectively, and looped around, or otherwise inserted Ithrough `a second set of holes, 'not s'hown,-'extendingthrough parts 20, 21 and 23, keepingithe parts positioned *together such that the effective length of the device is a minimum. When the device is'to be installed, the "brake shoes are 'moved 'to their full retractedpositions andthe -Wire or position of the'wire inserted through holes in parts '20, 21 kand 23 is removed '-andmember 21 -is screwedout until the center-to-center distance'fof pins "26 corresponds to the distance between the receiving-"apertures lin the brake shoes 11 and 12. Pins 26 are inserted into their receiving apertures and Vare'ilock-edin place by the insertion of the snap rings 27. Thereafter-the remaining portion of the wire is rekmoved 'from holes^44, l45 and 46 and rubber plugs 47 areinstalled :in J'all four holes in the tube 20 to seal --out waterfand dirt. 4The device will automatically adjust'itself aspreviously described and is ready for use. `'iWhilelthe `members 21, 22'have been described as both lbeing slidably lmounted in the tube 20, the invention will *function satisfactorily if one of the members 21, 22 'is"zlxed-vith respect to, or formed integral with tube 20,' and'fthe'other-slidable so long as a long, well over- A`lapping,*sliding connection is maintained, thereby avoid- `ing anyfsagging, etc. of the iparts which might tend to interferewith theirfree and easy operation.

:Vl/'bile the #preferred embodiment of the invention has beenf'describedin considerable detail, I do not Wish to be limited-to theparti'cular vconstruction shown which may ibe 'varied within 4the scope of the invention, and it is Athe intention "to-'cover hereby all adaptations, modificaz-tions and arrangements thereof Awhich come within the practice of those skilled Vin the art Ato which the invenl-tionfrelates A*Having thus -described 'my invention, I claim:

1. A brake adjusting device comprising a sleeve, arst and/second'member supported in said sleeve 4at opposite 'ends-thereof and `at least one of which is slidingly sup- 4ported by'said sleeve, VVa third member threaded into said rst member and extending toward said second member,

4-oneoftsaidsecond'and third members being provided with anen'larged' axially extending counterbore having an end surface spaced apart from the end of said member facing said other member and having an axially extending hole of smaller diameter extending between the end surface of said counterbore and said end of said member, the other of said members having an axially extending rod projecting toward the other member, a cup-shaped tubular cylinder telescoped over the end of said rod to form a Huid chamber and extending into said axially extending hole, the end of said cylinder extending into said counterbore a predetermined distance when said second and third members are in abutting engagement with each other, a fluid having a low boiling point ternperature in said chamber, spring means connected between said iirst and third members to thread said third member relative to said first member in a direction toward said second member, a fourth member in said counterbore, and means biasing said fourth member toward said end surface of said counterbore to prevent advancement of said third member by said spring means when said fourth member engages the end of said cylinder.

2. In a brake clearance adjusting device, first and second members supported for relative reciprocable movement toward and from each other, a third member adjustably connected to said first member for movement toward said second member, said second and third members having lixed abutments thereon limiting said relative reciprocable movement therebetween in the direction to ward each other, means operatively connected to said lirst and third members biasing said third member for movement relative to said first member in a direction to effect said adjustment, and means including temperature responsive means operatively associated with said second and third members and responsive to said relative reciprocable movement of said iirst and second members and to temperature changes for selectively holding said third member against movement relative to said first member by said tirst-named means.

3. A brake clearance adjusting device as claimed in claim 2 wherein said temperature responsive means comprises a bimetallic member.

4. A brake clearance adjusting device as claimed in claim 2 wherein said temperature responsive means comprises a bellows-type container having a low temperature boiling point liquid therein.

5. A brake clearance adjusting device as claimed in claim 2 wherein said temperature responsive means comprises a telescoped member closed at opposite ends and having a low temperature boiling point liquid therein.

6. in a brake clearance adjusting device, iirst and second members supported for relative reciprocable movement toward and from each other, a third member threaded to said irst member for adjustment toward said second member, said second and third members having fixed abutments thereon limiting said relative reciprocable movement therebetween in the direction toward each other, spring means operatively connected to said first and third members biasing said third member for rotation relative to said iirst member in a direction to effect said adjustment, and abutment means including temperature responsive means operatively associated with .said second and third members and responsive to said relative reciprocable movement of said first and second members and to temperature changes for selectively holding said third member against rotation by said spring means relative to said first member.

7. A brake clearance adjusting device as claimed in claim 6 wherein said temperature responsive means comprises a bimetallic member.

8. A brake clearance adjusting device as claimed in claim 6 wherein said temperature responsive means comprises a bellows-type container having a low temperature boiling point liquid therein.

9. A brake clearance adjusting device as claimed in claim 6 wherein said temperature responsive means comn prises a telescoped member closed at opposite ends and l tl having a low temperature boiling point liquid therein.

l0. A brake adjusting device comprising a sleeve, a iirst and a second member connected by said sleeve for relative reciprocable movement toward and from each other, a third member threaded into said rst member and projecting therefrom toward said second member, means on said second and third members limiting relative movement therebetween in the direction toward each other, spring means connected between said tirst and third members biasing said third member for rotation relative to said rst member in a direction to move said third member toward said second member, one of said second and third members being provided with an enlarged axially extending counterbore having an end surface spaced from the end of said member facing said other member and having an axially extending aperture of smaller diameter extending between said end surface of said counterbore and said end of said member, the other of said members having a projection extending into said aperture and comprising abutment means extending into said counterbore a predetermined distance when said second and third members are at the limit of their movement toward each other, a fourth member reciprocable in said counterbore, means biasing said fourth member toward said end surface of said counterbore and into engagement with said abutment means for holding said third member against rotation by said spring means relative to said lirst member while said abutment means projects into said counterbore, and means in said projection including means responsive to a raise in temperature for moving said abutment means relative to said member of which it is a part in the direction of said fourth member.

11. A brake clearance adjusting device as claimed in claim 10 wherein the means responsive to a rise in temperature is a low temperature boiling point liquid within a bellows-type container.

12. A brake clearance adjusting device as claimed in claim 10 wherein the means resopnsive to a rise in temperature is a telescoped member closed at opposite ends yand a low temperature boiling point liquid within a chamber formed by two telescoped tubular members having their opposite ends closed.

References Cited in the ile of this patent UNITED STATES PATENTS 

